1. Field of the Invention
The present invention relates to an electrochemical energy storage device and a method for operating an electrochemical energy storage device.
2. Description of Related Art
Lithium-ion accumulators are currently used to obtain high energy densities which, as high-energy accumulators, have energy densities of approximately 200 Ah/kg. They achieve energy densities of up to approximately 100 Ah/kg as high-power accumulators. The service life of such lithium-ion accumulators is currently generally six years maximum.
However, in particular for applications in electric and hybrid vehicles, the service life of lithium-ion accumulators used today is inadequate. In order to be able to economically operate and manufacture a vehicle of this type, it is necessary that the service life of the lithium-ion accumulator is in the range of 12 to 16 years.
For increasing the service life of an accumulator it is known from published European patent document EP-A 0 602 984 to use polycarbon disulfide as the cathode material which is not subject to polymerization or depolymerization during oxidation and reduction, i.e., the charge and discharge process of the accumulator. For example, lithium is also mentioned as the material for the anode. The service life of the accumulator is increased due to the fact that the cathode is not subject to polymerization and depolymerization. The disadvantage of the accumulator known from published European patent document EP-A 0 602 984 is that the anode is unprotected. This represents the limiting factor for the accumulator's service life.